'260 Transactions of the Boyal Society of South Africa. 
Origin ajid Method of Conserving the Material. — The numerous speci- 
mens on which these observations have been made came originally from the 
farm of Senator Southey at Culmstock, Schoombie, Cape Colony. They 
were fixed in warm 70 per cent, alcohol and are in an excellent condition 
for study. For the purpose of microscopical examination it is necessary 
to place the worms in glycerine, but the passage from one fluid into the 
other must be made with the greatest care, otherwise the specimens are 
apt to get contorted and disfigured. I therefore added glycerine to the 
alcohol in the proportion of 3 c.cm. to each 100 c.cm., and then allowed 
10 c.cm. of this mixture to evaporate slowly in a watch-glass. In warm 
weather after eight or ten days the alcohol is nearly completely evaporated 
and the specimens can be embedded in glycerine-gelatine, and then the 
cover-slip can be sealed with varnish in the usual fashion. 
Certain organs, such as the male genital canal, can be better demon- 
strated by means of a very weak solution of carmine, which is allowed to 
act till a sufficient degree of staining is reached. 
External Shape. — For the purpose of measuring the length of the 
Strongylus, specimens were chosen which showed the least degree of 
incurvation ; it was found that males vary between 4| to 5 mm., females 
from b\ to 6 mm. in length. In the male and female the breadth varies 
'between 100 and 120 fx. It is not possible to give more exact figures, 
because slight irregularities in the contour are present even in the best- 
preserved specimens. 
In both sexes the body gradually tapers towards the head ; the anterior 
profile appears to be slightly convex ; six minute conical papillae can be 
made out by means of high-power lenses. 
The body of the female (Fig. 2) begins to taper slightly a short distance 
from the uterus ; the taper increases after the anal region and then ends 
in a curved point. 
The male (Fig. 1) possesses a bursa copulatrix of conical shape ; in 
fixed specimens the edges of the pouch are more or less folded to the 
inside, and often several superposed folds are discernible. The dorsal 
margin of the pouch shows an outstanding median obtuse lobe ; the 
ventral portion is always more or less creased. In examining a great 
number of specimens there is no difficulty in finding females which are 
only slightly curved, whilst in males, as a rule, the terminal portion of 
the body with the bursa is bent in the shape of a hook. In males it is 
noticeable that the longitudinal axis is usually twisted, for which reason it 
is not easy to place the worm in a lateral position, therefore I have often 
found it advisable to separate the posterior extremity from the body, and 
lifting the cover-slip with a fine capillary to rotate the portion into a 
position suitable for study. 
Alterations of the profile, consisting in shrinking and bulging, 
